Thermostatic circuit interrupter



June 17, 1941.

P. R. LEE- `2,246,309

THERMOSTATIC CIRCUIT INTERRUPTER Filed Aug. 5, 1938 2 Sheets-Sheet 1 INVENTOR Paul BJLee.

June 17, 1941. P R, LEE 2,246,309

THERMOS TATIC CIRCUIT INTERRUPTER Filed Aug. 3, 1938 2 amis-sheet 2 Fig 5i. Fig 2 74 58 6'0 3 5? j [Hsu laiton 5'? \Fig Fly 61'60 Insulation 64 76* Insulonfum Insulation 69 Fry 9.- 52 Insulation;

072g--. l" 'fmw/-n A ?6\L wlTNl-:ssEs: 60/ QF'V" lNvENToR @MM5 SMM Paul RLee. w 1 [Hsuliion 52 BY l ATTORNEY Patented June 17, 1941 UNITED sTATEs PATENT oFFlcE 2.246.309 THERMOSTATIC CIRCUIT IN.IEEBUEWIILl.

Paul R. Lee, Mandelli, hlo, assigner to Westinghouse Electric a Manufacturing Company, East Pittsburgh, Pa., a corporation oi Pennsyl- Appucauon Amat s, 193s, sex-iai No. 222,796

(ci. zoo-13s) comms.

- serious damage to the contacts. Accordingly, the

use of creep-type thermostats has been somewhat limited and retarded, especially in domestic appliances, such as roasters, wallie irons and the like.

It is, therefore, an object of my invention to provide a creep-type thermostat suitable for domestic appliances, or the like, and free ot any radio-interfering impulses by reason of being void of any iluttering action and having an increased contact separation.

A further object of my invention is to provide a creep-type thermostat having an appreciable operating differential and a positive contact pressure.

Another object of my invention is to provide a creep-type thermostat including two cooperating bimetallic members, one of which is adapted to produce an increased contact separation and a positive contact pressure.

A further object of my invention is to provide a creep-type thermostat including two cooperating bimetallic members adapted to ilex in opposite directions, for producing an increased contact separation and a positive contact pressure.

Another object of my invention is to provide a creep-type thermostat including two cooperating v bimetallic members, with one of the members mounted upon the other member and adapted to -bodily move therewith and to flex in an opposite direction with a given change in temperature.

A further object of my invention is to provide an inexpensive, rugged, manually adjustable creep-type thermostat capable oi operating without contact-fluttering.

A still further object of my invention is to provide a creep-type thermostat capable of op- Fig. 5 is a top plan view of a modiiied form oi the device embodying my invention;

Fig. 6 is a side elevational view of the device shown in Fig. 5; and

Figs. '1, 8 and 9 are end views of the device shown in Fig. 5, illustrating its various operating positions.

Referring to Figures 1 to 4, inclusive, I show a thermostat or circuit interrupter Ill comprising a supporting base or structure I2, a mounting frame I4, preferably formed of insulating material, flexibly attached to the base I2 by a resilient member I6, a main bimetallic member I8 insulatedly attached at one end thereof to the structure I2, a second bimetallic member attached to the mounting frame I4 and operativelyl associated with the main bimetallic member I8,

'l a plurality of adjusting members or screws 24 and 26 operatively associated with the frame and the second bimetallic member 20 for adjusting and varying the operation of the cooperating contacts 28 and 30, and another adjusting screw 22 operatively associated with the base I2 and the resilient member I6.

Generally speaking, and as hereinafter described in detail, the operation of the thermostat, after being operatively associated or conlas eratlng without contact-iiuttering due to vibration.

Other objects of my invention will either be pointed out specically in the course of the following description of a device embodying my invention, or will be apparent from such description.

In the accompanying drawings:

Figure 1 is a top plan view of a device embodying my invention;

Figs. 2, 3 and 4 are sectional views taken along the line II-II of Fig. 1 showing the device in its various operating positions;

nected to a circuit (not shown) by means of terminals 32 and 34, respectively associated with resilient member I6 and main thermostatic member I8, is substantially as follows: The circuit through the thermostat IG extends from terminal 32 through resilient member I6, second bimetallic member 20, contacts 30 and 28, and through the main bimetallic member I8 to the second terminal 34. Passage of current through the main bimetallic member It causes it to heat and flex downwardly substantially as shown by the arrow A (Fig. 2). In a similar manner, the second bimetallic member 2li i'lexes downwardly with an increased temperature thereof and biases the contact 30 against contact 28. Inasmuch as the ohmic resistanceof the second bimetallic member 20 is considerably greater than that of the main bimetallic member I8, the second bimetallic tive contact pressure between the contacts 28 and I0, as hereinafter set forth.

The downward movement of the second member 28 is limited by the adjusting screw 28. Accordingly, as the main bimetallic member I 8 continues to increase in temperature it continues to flex downwardly, separating the contact 28 from the contact 38. 'I'he second bimetallic member 28 will, upon separation of the contacts andthe interruption of current passing through the bimetallic members, cool more rapidly than the first member I8, whereupon such member will quickly straighten out and move upwardly towards the contact adjusting screw ,'24, resulting in an increased contact separation upon the disengagement of the contacts by means of the rst member. The first bimetallic member I8 will then be required to flex upwardly, upon cooling, a substantial distance before' engaging the contact 38 and reenergizing the circuit.

More specifically, the supporting structure or base I2, in this instance, comprises an upper :dat member 36 and a depending end portion 38. It is preferred that these portions be formed of an insulating material, such as a phenolic resin, or the like. Moreover, it is to be understood that such structure may be formed of any other suitable material. Although members 38 and 38 may be integral, if desired, a separate upper plate portion 38 is preferably rigidly attached to the depending portion 38 by means of suitable rivets 48. The adjusting screw 22 is threadedly inserted through the top plate portion 38 of the structure I2 to cooperate with and operatively adjust the relative position of resilient member I6 and mounting frame I4, as hereinafter described. If desired, the adjusting screw 22 may have an insulating button 23 located on its lower end to adequately insulate itk from the resilient member I8.

'Ihe mounting frame I4 is, in this instance, formed of an insulating material, such as a phenolic resin, or the like, into substantially a J- shaped member flexibly attached to depending member 38 of the supporting structure I2 by means of resilient member I8. The J-shaped mounting frame I4 has a plurality of threaded apertures 23 and 25 located therein, one on top f and one in the bottom extensionof such frame. The adjusting screws 24 and 28 are then operatively associated with the threaded apertures 23 and 25 to adjustably limit the movements of the second bimetallic member 28, substantially as hereinafter described. I

The member I4 is rigidly attached at one end thereof to the resilient member I8, in this instance, by means of a suitable rivet 42. The second end of the resilient member I8 is rigidly attached to the depending portion 38 of the supporting structure I2.V The resilient member I8 is positioned upon the depending portion 38 in such a manner that the adjusting screw 22, operatively associated with the supporting base or structure I2, operatively engages such resilient member. It, therefore, follows that the adjusting screw 22, through its cooperation with the resilient member I8, may readily adjust the relative position of the mounting frame I4 with respect to the base or structure I2.

The main bimetallic member I8 is, in this instance, a strip-type bimetallic member rigidly attached at one end to the lower face of depending portion 38 of supporting structure I2, preferably by rivets 48, and having contact 28 rigidly attached at its free end. The main bimetallic member I8 is constructed in such a manner and positioned upon the supporting base I2 in such a way that it will flex downwardly with an increased temperature thereof. It is, therefore, ob-

vious that inasmuch as the main bimetallicA member I8 is rigidly attached to the supporting structure I2 such bimetallic member will flex a given amount with respect to such supporting structure for given temperature changes of such bimetallic member. Such temperature changes may be due to the changes in the ambient or due to the passage of current through member I8, or both.

The second bimetallic member 28 is, in this instance, a three-legged snap-acting bimetallic member rigidly attached at one end thereof to the mounting frame I4, adjacent one end of resilient member I8, by means of rivet 42. The second vmember 28 has rigidly attached near its free end the second contact 88, which is operatively associated with the rst contact 28, attached to the main bimetallic member I8.

In addition, member 28 has a considerably higher ohmic resistance and is lighter in mass than member I8, whereby member 28 will heat faster and cool quicker than member I8. Further it is to be understood that the second bimetallic member 28 may be a snap-acting member as herein described or may be a fast-moving strip-type bimetallic member or any other suitable thermal responsive bimetallic device which will heat and cool faster than the first bimetallic member I8.

Inasmuch as the second bimetallic-member 28 is substantially smaller in mass than the iirst bimetallic member I8, as is obvious, and has a greater ohmic resistance than such first member, the common current passing through the ther- Amostat will then cause the second bimetallic metallic member 28 will bias the rstbimetallic member I8 downwardly, regardless of the direction of biasing action of the rst member,

causing such members to be moved downwardly with a. continued passage of current therethrough. However, the downward movement of the bimetallic member 28 is limited by the engagement of the free end of such member 28 with the adjusting screw 28.

It is obvious, therefore, that the downward biasing action of the second bimetallic member 28, which is substantially greater than the downward or upward biasing action of the rst bimetallic member I8, whether the rst member 28 be heating or cooling, respectively, results in a good contact between the contacts 28 and 38, and

. ensures a positive contact pressure therebetween during the engagement thereof between the operating limits of the second bimetallic member as determined by the adjusting screws 24 and 26.

It, therefore, follows that for the contacts 38 and 28 to become separated, the main bimetallic member I8-must continue its downward movement in response to an increased temperature. As the main member I8 increases in temperature, it will flex downwardly, causing the contact 28 to be separated from contact 38 substantially as shown in Fig. 3. Inasmuch as the passage of current through the second bimetallic member 28 is then discontinued, and inasmuch as the mass of the second member 28 is considerably less than that of the rst member I8, the second member will rapidly cool at a rate greater than that ofthe main bimetallic member I8. As the second :bimetallic member 28 cools, it will ilex upwardly, say with a snap action, being restrained by the adjusting screw 24, substantially as shown in Fig. 4. The first bimetallic member I8 will then be required to travel an additional distance, namely, that-distance thefcontact 30 travels between adjusting screws 28 and 24, bei'ore contact 28 can become reengaged with contact 30. However, with the passage of time, and as the main bimetallic member I8 cools, such member will flex upwardly, permitting the contact 28 to be reengaged with contact 30, which in turn permits current to pass therethrough, substantially as hereinabove described.

Itis, therefore, obviousthat the main bimetallic member I8 is adapted to dlsengage and reengage the contacts 28 and 30 in response to predetermined temperature conditions, and that the second bimetallic member 20, operatively associated therewith, is adapted to separate the contacts 30 and 25 an additional distance after disengagement, and also ensuresa positive contact pressure between the contacts during engagement thereof.

The adjusting screw 24 cooperates with the second bimetallic member 20 by limiting its upward movement. In addition, the adjusting screw 24 prevents the main-bimetallic member I8 from applying an excessive strain on the second bimetallic member 20, such as when the mounting frame I4 and second member 20 have been moved toward the first member il, in response to the movements of the adjusting screw 22, as hereinafter described.

The manually operable adjusting screw 22, operatively associated with the supporting structure portion 36 and the resilient member I6, is adapted through the cooperative action of resilient member I6, to bodily move the mounting frame I4 either away from or towards the main bimetallic member I8. When the adjusting screw 22 is rotated so as to force the mounting frame I4 downwardly or towards the bimetallic member I8, it is obvious that the contact 30, mounted on the second bimetallic member 20, willlikewlse be moved towards the main bimetallic member i8. and therefore, it follows that the main bimetallic member will disengage the contacts 28 and 30 at a temperature above tha-t which would cause separation of the contacts if the mounting frame wasl left in its original position. It is also apparent that the adjusting screw 22 may be rotated substantially counter-clockwise such a distance that the mounting frame I4 will be backed away from the main bimetallic member i8 such a distance that it would be impossible for the bimetallic member I8 to contact the second bimetallic member 28 or to reengage the contacts 28 and 3U. With the thermostat operable in such ways, it is obvious that such thermostat will function not only as a manually adjustable thermally operable circuit lnterrupter, but also as a manually operable switch.

When it is desired to emploir the thermostatic circuit interruptor I embodying my invention, such thermostat is operatively associated,through terminals 32 and 34, with the circuit (not shown) it is desired to control. In addition, the thermostat may be located in juxtaposition with an electrical heat-emitting device (notshownl that is controlled by the thermostat, permitting the temperature variations thereof to aid ln the operation of such thermostat. The adjusting screw 22 is then adjusted to a predetermined position to bodily move the mounting frame I and second bimetallic member 20, as hereinabove described, to cooperate with the main bimetallic member I8 in a manner already set forth.

With the thermostat connected to the circuit to be controlled (not shown), and assuming the bimetallic members to be cold, such bimetallic members will be located in an upper position (Fig. 2) and the current will pass therethrough, as hereinabove described. The second bimetallic member 2li will then cause the two members to be moved downwardly a predetermined disltance depending upon the setting of adjusting screw 28. tTlie'main bimetallic member I8 will then continue its travel with an increase in temperature, disengaglng the contacts 28 and 35 at a predetermined temperature value (Fig. 3). The second bimetallic member 2li will then cool olf and relatively quickly return to its upper position, as determined by the adjusting screw 24, resulting in a wide gap between the contacts 3l and 28 (Fig. 4). The circuit will thus be opened, permitting the controlled device (not shown) -to decrease in temperature simultaneously with the main bimetallic member I8. As such member cools, it will flex upwardly, reengaging the contacts 28 and 30 and reconnecting the controlled device in circuit, permitting the thermostat I0 to again opera-te in a similar cycle.

Referring to Figs. 5 to 9, inclusive, I show a modiiled form of device embodying my invention comprising a J-shaped supporting structure 52, a main bimetallic member 54 flexibly attached to the supporting structure 52 by means of a U- shaped resilient member 56, and a second bimetallic member 58 insulatedly attached to the free end of the main bimetallic member 54 and extending transversely thereof. Suitable terminals 68 are positioned near one end of supporting structure 52 and are respectively secured to spaced stationary contacts 52 by means of a suitable rivet 14. Movable contacts 64 are rigidly attached near the ends of the second bimetallic member 58 to cooperate with stationary contacts 62.

.The supporting structure 52 ls, in this instance, formed into a substantially .l-shaped configuration from a single sheet of metal. However, it is to be understood that the supporting structure may be made in any other suitable manner. The supporting structure 52 has insulatedly attached near the free end of the long leg thereof, a. plurality of terminals 60 and stationary contacts 52, as previously noted, and has attached at the free end of the short leg thereof one end of the resilient member 58. In addition, a manually operable controlling device 85, such as a set screw, is threadedly engaged with the supporting structure 52, and operatively associated with the main bimetallic member 54 and resilient member 55, at substantially their junction.

The main bimetallic member 54 is substantially a strip-type bimetallic member adapted to flex away from the main or long leg portion of the supporting structure 52 with an increase in temperature thereof. The bimetallic member 54 is rigidly attached to the J-end of the supporting structure 52 by the U-shaped resilient member 58. The resilient member 55 thus tends to bias the cooperative end of the bimetallic member 54 upwardly or towards the main portion of the supporting structure 52 and against the heatresponsive movement of bimetallic member 54 and cooperating manually operable controlling device 58. It, therefore, follows that the manually operable controlling device tl. when rotated clockwise, will force the resilient *1.1. ber t8 and the bimetallic member t downwardly to dis-rv will not cause the movable contact 5d to ege the stationary contact 52. With the thermostat operable in such ways, it is apparent t auch device may be considered as being a manually operable switching device in addition to having thermally controlled circuit interrupting characteristics. The second bimetallic member 583 is, in this instance, a strip-type bimetallic member which is rigidly attached to the free end of and extends transversely to, the main bimetalllc member 5d by means of a coupling device 3d. The coupling device t@ has the top portion thereof, which is in contact with bimetallic member it, somewhat rounded and is insulatedly attached to the main member t to permit the second bimetalllc member 5d to be tightly attached thereto, and to be insulated therefrom. The device tb is insulated from the first member be by means of suitable insulating washers ld and is rigidly attached thereto by being riveted over, as shown at l. The second bimetallic member 58 is mounted upon the main. bimetallic member 5d in such a manner that it will iiex in substantially an opposite direction to that of the main bimetalllc member for a given temperature change. In other words, with an increase in temperature, the main binetallic member 5d will ex downwardly or away from the stationary contacts t2, whereas the second bimetallic member will ex concavely upwardly or towards the stationery contacts d2. 'I'his arrangement of the cooperating bimetallic members et and E8 causes the contacts to be separated an additional cunt upon the disengagement thereof, as in the case of the structure shown in Figs. 1 to d, inclusive, in response to the main bimetallic member 5t, and ensures a positive contact pressurebetween the movable contacts et and stationary contacts 62 upon reengagement, as hereinafter described. In addition, the mass of the second bimetallic member 58 is substantially less than that of rst member 5d, as is obvious from inspection, so as to permit the second member to quickly return toits normal curvature upon the disengagement of the contacts and consequent cooling of member 5S, to ensure an additional separation of the contacts and to avoid any chattering action thereof.

The stationary contacts 62 are rigidly attached to the supporting structure 52 by means of suitable rivets 'il and are insulated from the supporting structure by means of suitable insulating members I6 and 18. In addition, the contacts are operatively associated with the respective terminals 60 through the cooperation of the common fastening rivets 16. Thel movable contacts 64 are rigidly and electrically attached to the second bimetallic member Il, preferably by being spot welded thereto near the free ends thereof.

It, therefore, follows that with one of the terminals S0 operatively associated with the circuit to be controlled, (not shown) the current flowing in such terminal will pass through the second bimetallic member bt and out through the second terminal 5B. Accordingly. it is obvious that the operation' of the second bimetallic member 58 will be directly responsive to the passage of current therethrough, whereas the bimetallic member 55, `which is heated from a heat-emitting apparatus (not shown) in. thermal relation with bimetallic member ed, will determine the relative positions between the movable and stationary contacts td and @2.

When operating the modified form of the device embodying my invention, as illustrated by thermostat titl, as shown in Figs. 5 to 9, inclusive, with the cooperative contacts o2 and et engaged, substantially as shown in Figs'. 6 and 7, the current flowing through the associated circuit (not shown) will pass through the second bimetallic member et. This passage of current ugh the bimetallic member 6d will cause such member to arc concavely with respect to the supporting structure 52, as shown in Fig. 9. The resulting curvature of the second bimetallic member 58 causes the movable contacts t to be biased against the stationary contact 82 and against either the upward or downward biasing action of the main bimetallic member et. The contact pressure between the cooperating contacts 62 and @il will, therefore, be increased.

the temperature to which the thermostat is responsive increases, the main bimetallic member 5d will flex downwardly while the second member 5d becomes arced, carrying the second bimetaliic member d8 therewith, it being understood that both members 54 and 58 may receive heat from an exterior surface. The cooperating contacts 62 and 64 will then be disengaged and separated by a certain distance. The current ping through the second bimetallic member bd will, therefore, be disrupted, permitting the bimetallic member 5S to return to its normally straight curvature, as shown in Fig. 8, produc ing an increased separation between the cooperating contacts t2 and 64. It is, therefore, apparent that the main bimetallic member 54 will be required to move upwardly an increased distance, corresponding to the amount of curvature or straightening of the second'bimet-allic member 58 before effecting the reengagement of the contacts B2 and 84, thereby preventing any fiuttering between such cooperating contacts.

It is understood that the temperature at which the contacts 62 and @t are disengaged or reengaged depends upon the relative position of the manually operable device B5 in cooperation with the upward biasing action of the resilient member 5S, which flexibly mounts or attaches the main bimetallic member 54 to the supporting structure 52.

It is, therefore, obvious that thedevice embodying my invention includes a main bimetallic member adapted to operate said device in response to predetermined temperature conditions in cooperation with a second bimetallic member operatively associated therewith adapted to engage and disengage the contacts in response to the movements of the main bimetallic member to separate the contacts an additional amount after disengagement and to ensure a. positive contact pressure between the contacts upon reengagement, and thereafter during engagement.

Various other modifications may be made in the device embodying my invention without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art andthe appended claims.

I claim asfiny invention:

1. A circuit interrupter comprising, in combination, normally engaging contact means for making vand breaking a circuit, a main heat-responsive member and a second heat-responsive member movable in the same direction upon an increase of temperature, means for causing separation of said contact means after a predetermined degree of travel together, said second member thereupon cooling and reversing its dlrection oi' movement more quickly than said main member to eiect further disengagement of said contact means.

2. A circuit interrupter comprising, in combination, a supporting structure, contact means for making and breaking a circuit, a main heat-responsive member attached at one end to said structure and movable to separate the lcontact means in response to predetermined temperature changes, and a second heat-responsive member attached at one end to said structure and movable towards contact-making position in response to said temperature changes and also movable to separate the contact means an additional distance upon cooling pursuant to interruption of the circuit in response to movement of said main heat-responsive member.

3. A circuit interrupter comprising, in combination, contact means for making and breaking a circuit, a main heat-responsive member mov.

able to separate the contact means in response to predetermined temperature changes, and a second heat-responsive member movable towards contact-making position in response to said temperature changes and also movable to separate the contact means an additional distance upon cooling pursuant to interruption of the circuit in response to movement oi' said main heat-responsive member.

4. A circuit interrupter including, in combination, a supporting structure. a mounting frame, means for exibly attaching said frame to the structure, a plurality of contacts, a main bime'- tallic member adapted to operate the contacts, and a second bimetallic member attached to said means and operatively associated with the main bimetallic member, said second member adapted to further separate the contacts after disengagement thereof and to insure a positive contact pressure between the contacts.

5. A circuit interrupter including, in combination, a supporting structure, a mounting frame, means for flexibly attaching said frame to the structure, a plurality oi contacts, a main bimetallic member adapted to operate the contacts, a second bimetallic member attached to said means and operatively associated with the main bimetallic member to move in the same direction to insure a positive contact pressure between the contacts, means for arresting such movement of said second bimetallic member to effect separation of said contacts, and adjustable means operatively associated with the frame and second member for adjustably limiting movement of the second member.

6. A circuit interrupter including, in combination, a supporting structure, a mounting trame flexibly attached to the structure, a plurality of contacts, a main bimetallic member adapted to operate the contacts, a second bimetallic member attached to the mounting frame and koperatively associated with the main bimetallic member, said second member being snap-acting and adapted to separatevthe contacts after disengagement thereof and to insure a. positive contact pressure between the contacts, and manually adjustable means comprising screws operatively associated with the frame and second member for adjustably limiting movement of the second member.

7. A thermostatic circuit interrupter including, in combination, a supporting structure, a mounting frame ilexibly attached to the structure, a main bimetallic member adapted to move in given directions with changes in temperatures thereof to operate the interrupter, a plurality of contacts, one of said contacts being attached to the bimetallic member, a second bimetallic' member attached to the mounting frame and operatively associated with the main member and justable means operatively associated with the'v the frame and second member for adjustably limiting movement of the second member, and a second manually adjustable means operatively associated with the supporting structure and the ilexibly mounted frame for adjustably moving the frame and operatively associated second bimetallic member with respect -to the irst bimetallic member ior regulating the operation oi' the circuit interrupter.

8. In a circuit interrupting device including, in combination, a supporting structure, a main bimetallic member ilexibly attached at one end to the structure and adapted to operate said device in response to predetermined temperature conditions, a plurality of contacts including stationary contacts attached to the structure and movable contacts operatively associated therewith, and a second bimetallic member attached at substantially its mid point to the free end of and extending at substantially right angles to the main member adapted partly by the inherent movement oi its two ends and partly in response to the movements of the main member to engage and disengage the contacts and further adapted to separate the contacts an additional amount after disengagement.

9. A circuit interrupter adapted to operate an electric circuit, including, in combination, a supporting structure, contact means for making or breaking such circuit, a main bimetallic member attached at one end thereof to the structure for separating the contacts in response to predetermined temperature changes, anda second bimetallic member attached to the free end of and extending at substantially right angles to the main member adapted to be positioned within the circuit, said second bimetallic member being movable towards contact-making position upon an increase in temperature and movable to separate the contact means an additional distance upon cooling pursuant to interruption of the circuit in response to movement of said main heatresponsive member.

PAUL R. LEE. 

